PROJECT SUMMARY Understanding neural-vascular communication is vital to clinical and basic research. Perivascular neuron (PVN) activity can drive cerebral blood vessel dynamics. However, the impact of vascular events on neural activity has been only sparsely investigated. Our lab has found that a population of PVNs in primary somatosensory cortex (SI) encode cerebrovascular activity in vivo. However, the nature of this encoding, and its anatomical organization, is untested. Vessel-to-PVN signaling may support vascular homeostasis and rich communication across systems. These signals are relevant for research using blood flow to map neural activity (e.g., fMRI). Investigating perturbations of this signaling may elucidate mechanisms of cerebrovascular disfunction (e.g., as in ischemia, Parkinson?s Disease, and M.S.). To analyze PVN encoding of vascular activity, I will use in vivo two-photon imaging of neural and vascular cells, and optogenetics to perturb vessels and analyze the PVN response. In Aim I, I will test the hypothesis that vascular-encoding PVNs occur commonly in SI, and their activity is organized by cortical layer and vascular compartment, by expressing calcium indicators (jRGECO1a) in neurons and (GCaMP6f) in vascular endothelia to image their activity simultaneously. My preliminary data identified spatially distinct calcium events in the vascular signal that predict subsequent PVN activity. In this paradigm, the frequency of vessel responsive PVNs will be categorized by their stereotyped activity and anatomical location. Preliminary data in our lab has also shown that selective optogenetic vascular drive can modulate PVN activity. In Aim II, I will test the hypothesis that PVNs driven by optogenetically evoked vascular diameter changes will also be organized anatomically by their activity, that and their response to endogenous vascular events will parallel their response to optogenetic vascular drive. I will optogenetically constrict SI blood vessels by driving endothelial channelrhodopsin, dilate them with smooth muscle halorhodopsin, and evoke natural tactile driven functional hyperemia, to analyze the responses of PVNs expressing GCaMP6s. In Aim III, I will test the hypothesis that PVN responses to optogenetically driven vascular activity can be pharmacologically perturbed by TRPV4 and adenosine A1 receptor antagonists, but that they are likely unaffected by blocking glutamatergic signaling. I will test this prediction by evoking PVN responses to optogenetic vascular activity as in Aim II, and by exposing SI cortex to receptor antagonists. Training Environment: This project will take place over three years in the Brown University Neuroscience Graduate Program under the mentorship of Dr. Christopher Moore. The Research Training Plan includes didactic professional, technical, and science writing training, as well as hands-on technical seminars.